1. Technical Field
The present disclosure relates to energy delivery feedback systems and, more particularly to thermal feedback systems for electrosurgical energy systems and methods of their use.
2. Background of Related Art
The use of electrical energy including radiofrequency and microwave energy (“RF & MW energy”) and, in particular, radiofrequency electrodes or microwave antennae (“RF-electrodes/MW-antennae”) for ablation of tissue in the body or for the treatment of pain is known. Generally, such RF electrodes (e.g., probes, resistive heating elements and the like) include an elongated cylindrical configuration for insertion into the body to target tissue which is to be treated or ablated. The RF electrodes can further include an exposed conductive tip portion and an insulated portion. The RF electrodes can also include a method of internal cooling (e.g., a Cool-tip™ or the like), such as the RF electrodes shown and described in U.S. Pat. Nos. 6,506,189 entitled “COOL-TIP ELECTRODE THERMOSURGERY SYSTEM” issued to Rittman, III et al., on Jan. 14, 2003 and 6,530,922 entitled “CLUSTER ABLATION ELECTRODE SYSTEM” issued to Cosman et al., on Mar. 11, 2003, the entire content of which is incorporated herein by reference. Accordingly, when the RF electrode is connected to an external source of radiofrequency power, e.g., an electrosurgical generator (device used to generate therapeutic energy such as radiofrequency (RF), microwave (MW) or ultrasonic (US)), and current is delivered to the RF electrode, heating of tissue occurs near and around the exposed conductive tip portion thereof, whereby therapeutic changes in the target tissue, near the conductive tip, are created by the elevation of temperature of the tissue.
In some applications, for example, tumor ablation procedures, multiple electrodes are inserted into the body in an array to enlarge ablation volumes.
In a particular application, arrays of high frequency electrodes are inserted into tumors. The electrodes are typically placed in a dispersed fashion throughout the tumor volume to cover the tumor volume with uniform heat. The multiple electrodes may be activated simultaneously or sequentially applied with high frequency energy so that each electrode heats the surrounding tissue. During series activation, energy is applied to each electrode one at a time. This sequence of cycling the energy through the electrodes continues at a prescribed frequency and for a period of time.
The electrode systems discussed above are limited by the practical size of lesion volumes they produce. Accordingly, electrodes with cooled conductive tips have been proposed. With cooling, radiofrequency electrode tips generally produce larger lesion volumes compared with radiofrequency electrodes, which are not cooled. For example, standard single cylindrical electrodes, with cooled tips, as described above, may make lesion volumes up to 2 to 3 cm in diameter in living tissue (e.g., the liver) by using needles of 1 to 2 mm in diameter and having exposed tip lengths of several centimeters.